Function to sort the names of basketball players - c

Question

I need to write a program that will recieve (from the user) the number of players in a basketball team and then I need to create an array in a dynamic way. The program will sort the array in an alphabetic order and then print it like that aswell.
I wrote this code:
#include <stdio.h>
#include <stdlib.h>
#include <malloc.h>
#include <string.h>
#define LENGTH 20
int main(void)
{
int numplayers, i, j;
char persname[LENGTH], tname[LENGTH], temp[LENGTH];
printf("Please insert the amount of basketball players in the group\n");
scanf("%d", &numplayers);
char **players = (char **) malloc(numplayers * sizeof(char *));
printf("Please insert the names of your %d basketball players\n", numplayers);
for (i = 0; i < numplayers; i++) {
gets(persname);
strcpy(persname[i], tname[i]);
}
for (i = 0; i < numplayers-1; i++) {
for (j = i+1; j < numplayers; j++) {
if (strcmp(persname[i], persname[j])) {
strcpy(temp[i], persname[i]);
strcpy(persname[i], persname[j]);
strcpy(persname[j], temp);
}
}
}
for (i = 0; i < numplayers; i++) {
printf("%s\t\t%s\n", tname[i], persname[i]);
}
return 0;
}
But when I run the code, I get an error right after typing the amount of players in the team, Unhandled exception at 0x507340E3 (msvcr120d.dll) in Question4.exe: 0xC0000005: Access violation reading location 0xFFFFFFCC.
What did I do wrong.

Answer 1

Your loop that inputs all the names doesn't use players. Instead it uses pername and tname, incorrectly. This line:
strcpy(persname[i], tname[i]);
shouldn't compile, you're mixing up types in a way that just doesn't make any sense. You should input a line, then dynamically allocate new memory into players[i] and copy the input there. If you have strdup(), that's what it's good for.
Basically the input loop should be something like:
for (i = 0; i < numplayers; i++)
{
char line[1024];
if(fgets(line, sizeof line, stdin) != NULL)
{
const size_t len = strlen(line);
players[i] = malloc(len + 1);
if(players[i] == NULL)
{
fprintf(stderr, "**Out of memory!\n");
exit(1);
}
memcpy(players[i], line, len + 1);
}
else
fprintf(stderr, "**I/O error!\n");
}
This uses fgets() which is way safer than the horribly never-to-be-used gets() monster.
Also, you're not allocating any room for the individual names, just for the array of string pointers.
This line:
char** players = (char**)malloc(numplayers*sizeof(char*));
can be simplified to the much clearer:
char** players = malloc(numplayers * sizeof *players);
No need to repeat type names, and no need to cast the return value of malloc().

Answer 2

I managed to solve it! :)
Here is my updated code:
#include <stdio.h>
#include <stdlib.h>
#include <malloc.h>
#include <string.h>
#define LENGTH 20
#define LENGTH2 20
int main(void)
{
int numplayers, i, j;
char persname[LENGTH][LENGTH2], temp[LENGTH];
printf("Please insert the amount of basketball players in the group\n");
scanf("%d", &numplayers);
char** players = (char**)malloc(numplayers*sizeof(char));
printf("Please insert the names of your %d basketball players\n", numplayers);
for (i = 0; i < numplayers+1; i++)
{
gets(persname[i]);
}
for (i = 1; i < numplayers+1; i++)
{
for (j = 1; j < numplayers+1; j++)
{
if (strcmp(persname[j - 1], persname[j]) > 0)
{
strcpy(temp, persname[j - 1]);
strcpy(persname[j - 1], persname[j]);
strcpy(persname[j], temp);
}
}
}
printf("\nBasketball players names in order are : ");
for (i = 0; i < numplayers+1; i++)
{
puts(persname[i]);
}
getch();
free(players);
system("PAUSE");
return 0;
}